The control of gene expression and the structure of chromatin in mammalian tissues is based upon interactions of the constituent macromolecules of nucleohistone. This project is designed to investigate histone-histone and histone-DNA interactions responsible for aspects of chromatin conformation. Alterations of these interactions probably play a role in mediating the control of gene expression. These associative interactions will be studied by various physical methods; and will use histone fractions prepared in a new fashion which, unlike previous studies, does not result in conformational denaturation. Extensions in ultracentrifuge and electrophoresis methodology are planned which should facilitate this study.